Method of producing scratch resistant polymer compositions

ABSTRACT

Filled polymer compositions having improved scratch resistance comprise as a major component a polymer resin blend itself comprising 70 to 95% polypropylene homopolymer, and 5 to 30% low density polyethylene, particularly lldpe or vldpe; and 5 to 30% plate like inorganic filler. Optional components include high rubber ethylene-propylene copolymers, fatty acid amides, polyorganosiloxanes and epoxy resins as well as pigments, antioxidants etc. The compositions are formed by mixing the plate like filler and the epoxy resin prior to mixing with another component of the composition which is significantly absorbed by the plate like filler, and subsequently mixing the components of the composition in the melt phase, particularly in a twin screw extruded, and extruding the composition. The compositions find use in vehicle interior trim components, which particularly include polyorganosiloxane, and domestic appliance components, particularly housings, which particularly include high rubber ethylene-propylene copolymer.

This invention relates to scratch resistant polymer compositions andmoulded articles made using such compositions. In particular it relatesto such pigmented compositions and articles having aesthetic appeal forexample vehicle interior trim components and domestic appliancecomponents, particularly housings.

Plastics materials are used in many applications where aestheticappearance is important. Indeed, the commercial success of such articlesmay depend on their aesthetic appeal. In addition, such articles shouldalso possess suitable functional properties.

To maintain a good appearance, it is desirable that plastic articleshave good scratch resistance and do not optically stress whiten to anysignificant extent when scratched. Stress whitening of pigmented plasticarticles is aesthetically undesirable because the white marks formed onscratching visually contrast with the colour of the article. This isparticularly marked if the plastics article is darkly pigmented forexample black, grey, brown or blue, as are commonly used in vehicleinterior trim.

Our PCT Application No PCT/GB 92/01400, (published as WO 93/03095 A)(which is incorporated by reference herein) relates to a polypropylenecopolymer composition and to articles made from it having improvedscratch resistance and including a polyorganosiloxane, particularly apolydimethylsiloxane. This prior development provides an improvement inscratch resistance over conventional compounded polypropylene typematerials, but further improvements would be very attractive forindustrial uses of compounded polyolefin materials.

The present invention is directed to a filled compounded blend of mainlypolypropylene and a minor proportion of low density polyethylene typepolymers, in which the filler is mainly a plate like filler such astalc. The filled compounded blend has excellent scratch resistance,retains a desirable combination of impact strength and stiffness and maybe produced economically.

Accordingly the present invention provides a filled polymer compositionwhich comprises:

as a major component a polymer resin blend itself comprising:

from 70 to 95% by weight of a polypropylene homopolymer, and

from 5 to 30% by weight of a low density polyethylene; and from 5 to 30%by weight of a plate like inorganic filler.

The compositions of the invention can give significantly improvedresistance to stress whitening and can be used to produce mouldedarticles with surfaces having improved scratch resistance. Accordingly,a further aspect of the invention provides for the use of a polymercomposition according to the invention as a scratch resistant material.

The polypropylene homopolymer used in the polymer resin blend is aconventional substantially isotactic polypropylene. Typically it willhave a MFI of from 2 to 50, more usually 4 to 40 and commonly 5 to 20,dg.min⁻¹ (at 230° C., 2.16 kg load). As is described in more detailbelow, within the invention there are compositions having differingrelative levels of filler. We have found that within the overall MFIranges different ranges are appropriate to such different filler levelsas is set out below.

The low density polyethylene used in the polymer resin blend is apolyethylene having a density in the range about 0.890 to about 0.935.This range corresponds the polymers commonly described as Low DensityPolyEthylene (LDPE) and Very Low Density PolyEthylene (VLDPE). AmongLDPE polymers, so-called Linear Low Density PolyEthylene (LLDPE)polymers are particularly useful. The MFI of the low densitypolyethylene polymer is typically from 2 to 40, more usually from 4 to35 and most commonly from 15 to 25, dg.min⁻¹ (at 190° C., 2.16 kg load).

Considered as a two component blend, the polypropylene and low densitypolyethylene are used in relative proportions within the range about 70to about 95% by weight polypropylene and about 30 to about 5 by weightpolyethylene, more usually 80 to 90% polypropylene and 20 to 10%polyethylene and most commonly about 85% polypropylene and polyethylene.

The "plate like filler" is a filler whose particles have a length andwidth substantially greater than their depth. The presence of a platelike inorganic filler in the composition of the invention gives thecomposition enhanced stiffness. Suitable plate like inorganic fillersinclude mineral fillers such as clays, mica and especially talc.Particularly useful talcs include Luzenac 15M00 and 20M00S (Talc deLuzenac) and Finntalc M03 from Finnminerals Oy. Although clays haveplate like particles and can be used in the invention, their use alonein not especially desirable. The composition can include mixtures ofplate like fillers and/or other, non plate like, fillers such as chalk,for example Polycarb SB ground chalk filler form ECC International, ormilled glass fibre, for example Vetrotex 1320 unsized milled glass fibrefrom Vetrotex. The filler desirably has an mean particle size (measuredas spheres of equal diameter) of from 1 to 20 μm. With anisotropicfillers such as the plate like filler the maximum dimensions ofindividual filler particles will generally be significantly larger thanthe mean.

The amount of plate like filler used is suitably from about 5 to about30% by weight of the composition. In general, the filler level invehicle interior trim applications is typically in the range 14 to 30%,particularly 16 to 25, and especially about 18 to 22%, by weight of thecomposition. At these filler levels the polypropylene used is desirablyone having a MFI of typically from 10 to 50, more usually from 10 to 40and most commonly 10 to 25, dg.min⁻¹.

The filler level in domestic appliance applications, particularlyhousings for domestic appliances, is typically from 5 to 15%,particularly 7 to 12%, especially about 10%, by weight. At these fillerlevels the polypropylene used is desirably one having a MFI of typicallyfrom 2 to 15, more usually from 4 to 15 and most commonly 5 to 15,dg.min⁻¹.

Usually the filler will be mostly or wholly the plate like filler, butother fillers can be included. Usually, when non plate like fillers areincluded the amount will be up to about 5 weight % of the composition.The inclusion of such other fillers may have a deleterious effect onsome properties. However, for vehicle interior trim applications, wehave found that a particularly useful filler combination is talc 19 to25% and chalk 1 to 3 weight % of the composition.

Compositions of the three components have good scratch resistance, butwe have found that even better results can be obtained by also includinga polyorganosiloxane in the composition. When used thepolyorganosiloxane is of a type and is used in amounts broadly similarto those set out in PCT/GB 92/01400 referred to above. For full detailsof the use of polyorganosiloxanes, reference is directed to thatspecification. However, the polyorganosiloxane is typically apolydialkylsiloxane, and particularly a polydimethylsiloxane. To getgood compatibility with the polymer composition, the viscosity of thepolyorganosiloxane will typically be from 13000 to 50000, particularly25000 to 35000, and optimally about 30000, cSt at 25° C. Suchpolyorganosiloxanes typically have molecular weights up to 95 kD,particularly 65 kD to 90 kD especially 80 kD to 88 kD for example 85 kD.Generally, compatibility is best when relatively viscouspolyorganosiloxanes are used with resin polymers having low MFI andrelatively fluid polyorganosiloxanes are used with resin polymers havinghigh MFI. The polyorganosiloxanes can be provided to the polymercomposition as the siloxane itself (usually an oily liquid) or as amasterbatch for example in polypropylene. Examples of suitablepolyorganosiloxanes include Nourimix SI-702 (a 30% polyorganosiloxanemasterbatch in polypropylene) (Akzo) or Rhodorisil 47V/30000(Rhone-Poulenc).

When used in the polymer composition of this invention, the amount ofpolyorganosiloxane will usually be at least 0.5% by weight based on theoverall composition. The use of less gives little benefit in improvingscratch resistance. The performance of the compositions improves withincreasing polyorganosiloxane amount up to about 2 weight % of thecomposition. Amounts larger than about 2.5 weight % offer little furtherbenefit and it is unlikely that amounts greater that about 5 weight %will be used because of the cost of the polyorganosiloxane and suchlarge amounts may have an adverse effect on the mechanical properties ofthe composition. We have obtained best results using from 1.5 to 2 andparticularly about 1.5 weight % of polyorganosiloxane. The use of apolyorganosiloxane is particularly applicable to compositions containingrelatively high levels of plate like filler, such as those discussedabove for vehicle trim applications. For domestic applianceapplications, a polyorganosiloxane can be included, but may have anadverse effect on gloss and the improvement in scratch resistance isless significant in a practical sense.

Rather surprisingly, we have found that the inclusion of high rubberpolypropylene ethylene copolymers can have useful effects incompositions of the invention. These polymers are, in effect, blends ofethylene propylene rubber and isotactic polypropylene. The expectedeffect of including such materials would be an increase in toughness anda sharp increase in susceptibility to stress whitening and thus areduction in scratch resistance. Although we have observed the increasein toughness, the stress whitening is increased less than would havebeen expected. Further, at relatively low filler levels, the inclusionof high rubber polypropylene ethylene copolymers appears to give anincrease in the gloss of moulded products. This is unexpected and isbeneficial in making products more attractive to the consumer,particularly for domestic appliances. At higher filler levels, as aretypical for vehicle interior trim uses, the increase in gloss is muchreduced and may not be observed at all. We cannot explain this, but itis particularly convenient that the demand in such materials is forrelatively low gloss levels.

When used the high rubber polypropylene ethylene copolymers willtypically comprise from 5 to 40%, particularly 10 to 28%, especially 11to 16% by weight as such based on the combination of the polypropylenehomopolymer, polyethylene and high rubber polypropylene ethylenecopolymers. The rubber levels in the copolymers is typically from 12 to50%, particularly 20 to 45, and especially about 43% by weight on thecopolymer. The rubber and addition levels will usually be chosen to giveabout 2 to about 15%, particularly 5 to 8%, by weight ethylene propylenerubber based on the total polymer.

In calculating the overall proportions of polypropylene andpolyethylene, the polypropylene in the high rubber polypropyleneethylene copolymer should be included in the calculation. In other wordsit is clearer to express the addition of the high rubber polypropyleneethylene copolymer in terms of the ethylene propylene copolymer rubberincluded in the resin formulation.

Expected typical end uses for the compositions of the invention inmoulded form include automotive interior trim components and domesticappliances. Almost invariably these are pigmented and, thus, the polymercompositions of the invention will ordinarily be pigmented. The amountof pigment in the composition will typically be from 0.1 to about 7,most usually 0.3 to 2.5 weight % of the composition, depending on thepigment used and the colour and tone required. Suitable pigments may beorganic and/or inorganic and include carbon black, titanium dioxide,iron oxide and copper phthalocyanine.

Conventional additives such as anti-oxidants, antioxidant synergists,neutralising agents, lubricants, ultra violet light stabilisers andmould release agents can be included in the composition. Examples ofsuch additives include, as anti-oxidants hindered phenols such asIrganox 1010 (Ciba Geigy), typically in an amount of 0.05 to 0.7%especially 0.1 to 0.2%; as antioxidant thioester synergistsdilaurylthiodipropionate and distearylthiodipropionate in an amount of0.05 to 1%; as neutralising or antacid agents, materials such asaluminiummagnesium hydroxy stearate, typically in an amount of 0.05 to0.8%; as lubricants, metal, for example zinc and calcium, stearates,which may also act as antacids; and as ultra violet light stabilisers,hindered amine stabilisers such as Tinuvin 770DF (Hoechst) or Chimassorb944 (Ciba Geigy) typically in an amount of about 0.8% (all percentagesbeing by weight based on the composition).

Fatty acid amides are commonly used as mould release agents and can beused as such in the composition. However, we have found that thecombination of polyorganosiloxane and fatty acid amide gives especiallygood effect on scratch resistance. The effect seems to be synergisticand we do not know why it is so beneficial.

Accordingly, a further aspect of the invention provides a filled polymercomposition which comprises:

as a major component a polymer resin blend itself comprising:

from 70 to 95% by weight of a polypropylene homopolymer, and from 5 to30% by weight of a low density polyethylene; from 5 to 30% by weight ofa plate like inorganic filler; and a fatty acid amide.

The effect of including a fatty acid antide component is to enhancefurther the improvement in scratch resistance. Suitable fatty acidamides are of fatty acids with C10 to C25, especially C16 to C22, carbonchains. A particularly suitable fatty acid amide is erucamide, availableas Crodamide E (Croda Chemicals). The amount of fatty acid amide willusually be up to 1 weight % of the composition, particularly 0.1 to0.8%, and especially about 0.5% by weight of the composition.

The plate like inorganic filler may tend to absorb certain components inthe polymer composition on forming the composition. In particular talctends to abstract antioxidants from the polymer composition thusrequiring an increased amount of antioxidant to be used. In thisinvention, we have additionally found that the plate like filler canabsorb polyorganosiloxane when present. To counteract these effects, itis generally desirable to use a plate like filler that has beenpassivated. Various ways of passivating fillers have been suggested, butwe have found it particularly useful to passivate the filler by theinclusion of an epoxy resin. The use of epoxy resins can reduce both ofthese effects very considerably. The use of passivated plate likefillers forms a particular aspect of the invention, especially when thefiller is passivated by the inclusion of an epoxy resin.

Thus, in a further aspect the invention provides a filled polymercomposition which comprises:

as a major component, a polymer resin blend itself comprising:

from 70 to 95% by weight of a polypropylene homopolymer, and

from 5 to 30% by weight of a low density polyethylene; and from 5 to 30%by weight of a plate like inorganic filler; and an epoxy resin.

Desirably the composition also includes a fatty acid amide as describedabove and, accordingly, the invention further includes a filled polymercomposition which comprises, as a major component, a polymer resin blenditself comprising:

from 70 to 95% by weight of a polypropylene homopolymer, and

from 5 to 30% by weight of a low density polyethylene; and from 5 to 30%by weight of a plate like inorganic filler; a fatty acid amide; and anepoxy resin.

When used, the epoxy resin is typically present in the polymercomposition in an amount of from 0.1 to 2% by weight. Larger amounts donot provide any further improvement in the properties of the polymercomposition. Most desirably the epoxy resin is present in an amount of0.1 to 1.5 weight % and optimally about 0.4 to 1 weight %.

Suitably, the components of a polymer composition according to theinvention intended for vehicle interior trim applications are: the resinblend of polypropylene homopolymer and low density polyethylene ispresent in the composition in an amount of 70 to 86, particularly 75 to85% by weight,

within the resin blend the proportion of polypropylene is typically 70to 95%, particularly about 85%, by weight of a polypropylene polymerhaving an MFI of from 4 to 40, and the proportion of low densitypolyethylene is from 5 to 30%, particularly about 15%, by weight of lowdensity polyethylene having an MFI of from 4 to 35;

filler:

14 to 30 and particularly 16 to 25, especially 18 to 22 weight %,particularly of talc;

polyorganosiloxane:

0.5% to 2.5% and especially not exceeding about 2% and particularlyabout 1.5 weight %, especially of a polyorganosiloxane having aviscosity of about 30000 cSt;

fatty acid amide:

0.1 to 0.8% particularly about 0.5%;

epoxy resin:

0.1 to 1.5% and particularly 0.4 to 1%.

other additional components may be present particularly in the amountsas disclosed above.

Suitably, the components of a polymer composition according to theinvention intended for domestic appliance applications are: the resinblend of polypropylene homopolymer and low density polyethylene ispresent in the composition in an amount of 85 to 95, particularly 88 to93 and desirably about 90% by weight,

within the resin blend the proportion of polypropylene is typically 70to 95%, particularly about 85%, by weight of a polypropylene polymerhaving an MFI of from 4 to 15, and the proportion of low densitypolyethylene is from 5 to 30%, particularly about 15%, by weight of lowdensity polyethylene having an MFI of from 4 to 35;

optionally but desirably:

high rubber polypropylene ethylene copolymer in an amount to supply fromabout 2 to about 15%, particularly 5 to 8%, by weight ethylene propylenerubber based on the total polymer, particularly as high rubberpolypropylene ethylene copolymer containing 12 to 50%, particularly 20to 45, and especially about 43%, of ethylene propylene rubber by weighton the copolymer;

filler:

5 to 15 and particularly 7 to 12, especially about 10, weight %,particularly of talc;

fatty acid amide:

0.1 to 0.8% particularly about 0.5%;

epoxy resin: 0.1 to 1.5% and particularly 0.4to 1%.

other additional components may be present particularly in the amountsas disclosed above.

The compositions of the invention can be made by mixing the componentsof the composition. Initial formulation can be in a `dry` mixer, usuallywith the polyorganosiloxane being added as the last component, but fullcompounding will usually include melt phase processing typically underhigh shear as in a twin screw extruder. Thus, the invention includes amethod of making a composition of the invention by mixing the componentsof the composition in the melt phase, particularly in a twin screwextruder, and extruding the composition.

When used, an epoxy resin is included in the composition to passivatethe plate like filler towards additives such as antioxidants and towardsa polyorganosiloxane, when used. The effectiveness of the epoxy resin inpassivating the plate like filler towards the polyorganosiloxane isseverely reduced unless the filler is treated with the epoxy resinbefore contact with the polyorganosiloxane. We think that as thepolyorganosiloxane is liquid it is available to interact with the fillerimmediately on contact and passivation should be done before suchcontact. Passivation towards antioxidants and similar materials does notneed this precaution because epoxy resins are either liquid orrelatively low melting solids which readily melt in melt processing andas liquids will passivate the filler before the antioxidants melt.

Accordingly, the invention additionally provides a method of producing afilled polymer composition which comprises:

as a major component a polymer resin blend itself comprising:

from 70 to 95% by weight of a polypropylene homopolymer, and

from 5 to 30% by weight of a low density polyethylene;

from 15 to 30% by weight of a plate like inorganic filler;

at least 0.5% by weight of the polymer resin blend of apolyorganosiloxane; and

an epoxy resin,

which method comprises mixing the plate like filler and the epoxy resinprior to mixing with another component of the composition which issignificantly absorbed by the plate like filler, in particular apolyorganosiloxane and/or an antioxidant, and subsequently mixing thecomponents of the composition in the melt phase, particularly in a twinscrew extruder, and extruding the composition.

For compositions of the invention containing a polyorganosiloxane, aconvenient and advantageous practical way of including thepolyorganosiloxane in the composition is to formulate the compositionnot including the polyorganosiloxane up to and including part of meltphase processing, particularly in a twin screw extruder or similar highshear melt phase processor, and to add the polyorganosiloxane to thecomposition during such melt phase processing, for example by adding itthrough a port in the barrel of the extruder, and subsequentlycontinuing melt phase processing to thoroughly mix thepolyorganosiloxane into the formulation.

The polymer composition of the invention can conveniently be formed intoarticles such as vehicle interior trim components or domestic appliancecomponents, particularly housings, by injection moulding. Otherproduction techniques can be used as appropriate. The invention includesmoulded and fabricated components made from the polymer composition ofthe invention.

The invention is illustrated by the following examples. All parts andpercentages are by weight based on the total composition unlessotherwise indicated.

Materials Polymers

Polypropylene homopolymer--(PP) the polymers used were standardproduction isotactic polypropylene polymers (ICI Chemicals & PolymersLtd). Four polymers of different MFI values (measured at 230° C., 2.16kg load) were used:

    ______________________________________                                               PP-A          MFI  3.7                                                        PP-B          MFI  6                                                          PP-C          MFI 13                                                          PP-D          MPI 34                                                   ______________________________________                                    

Low Density Polyethylene (PE) the following polymers of differingdensities and MFI values (measured at 190° C., 2.16 kg load) were used:

i PE-A: Very Low Density Polyethylene: density 0.895, MFI 22.

ii PE-B: Very Low Density Polyethylene: density 0.895, MFI 4.6.

iii PE-C: Very Low Density Polyethylene: density 0.900, MFI 1.1.

iv PE-D: Linear Low Density Polyethylene: density 0.920, MFI 4.6.

Ethylene Propylene Rubber (EPR) Novolen 2900 NCX (BASF) a high rubberethylene propylene copolymer containing 43% by weight rubber (about 22%by weight ethylene), MFI 10 (measured at 230° C., 2.16 kg load). (NB incalculating the total amount of polypropylene in the mix with EPRpresent the PP in the EPR is included.)

Polypropylene Copolymer (co-PP) commercially available medium impactpropylene ethylene copolymer (about 12% rubber phase--about 6% ethyleneresidues), MFI 13 (measured at 230° C., 2.16 kg load).

Fillers

Luzenac 20 M00S (mean particle size ca 8 μm) and Luzenac Steamic 00S(mean particle size ca 5 μm) are high quality talcs (Talc de Luzenac).

Finntalc M03 high quality talc mean particle size ca 2 μm (FinnmineralsOy).

Polyorganosiloxane

PDMS--is Rhodorsil 47V/30000 (Rhone Poulenc)--a polydimethylsiloxaneviscosity 30000 cSt (±10%) and average molecular weight 85 kD which wasadded as an oil.

Additives

Irganox 1010--hindered phenol antioxidant (Ciba Geigy).

Tinuvin 770--hindered amine light stabiliser (Hoechst).

Chimassorb 944--hindered amine light stabiliser (Ciba Gigy).

DSTDP--distearylthiodipropionate, a thioester antioxidant synergist.

Hostanox 03--hindered phenol antioxidant (Hoechst).

Hostanox SE 10--non thioester antioxidant synergist (Hoechst).

Crodamide E--erucamide fatty acid amide (Croda Chemicals).

Araldite--epoxy resin, liquid or solid resins were used (Ciba Geigy).

Pigment--a mixture of carbon black and titanium dioxide to give a greycolour. Differing shades were used including Medium Grey and DarkGrey--a near black pigment formulation including blue pigment to give aneutral tone in the product.

Test methods Scratch resistance (SR) Two tests were used:

1 Sets of scratches were made on moulded test plaques of the polymercompositions using a hand operated scratch tester (No 706 from SheenInstruments Ltd. of Teddington, England). Applied forces in the range0.5 to 15N and a 1 mm hemispherical stylus were used. The scratches werevisually assessed by a set of independent observers and the test plaquesranked according to the visibility of the scratches (1 indicating theleast visible scratches). For Examples 1 and 4 four and for Example 3five observers were used. The rankings of the observers were averaged togive a mean ranking score (Mean Rank--TR) and the difference between themaximum and minimum rank for each sample was also noted as the range(Rg) as an indication of consistency between the observers and thedistinctness of the ranking scores. (This test is based on BS3900-E2).

For some samples a series of 10 lines was scratched as described aboveusing applied forces of 0.5, 0.7, 1, 2, 3, 5, 7, 10, 12 and 15N. Thescratches were examined to assess the number of lines of stresswhitening were visible. The result is given as the No of Lines (Lin).

Specular gloss (SG - %)--was measured at 60° of the smooth side ofmoulded test plaques according to ASTM DS23 - 85.

Tensile yield stress (TYS - MPa)--was measured according to ISO 527,with a rate of application of force of 50 mm/min.

Flexural Modulus (FM - GPa)--was measured according to ISO 178, with arate of application of force of 10 mm/min.

Melt Flow Index (MFI - dg.min⁻¹)--was measured according to ISO 1133 at190° C., for the unfilled polyethylene polymers, and at 230° C., for theunfilled polypropylene polymers and formulated mixes, using a 2.16 kgload.

Notched Izod (Izod - kJm⁻²)--was measured according to ISO 180 at thetemperatures stated with a machined notch radius of 0.25 mm.

Heat Distortion Temperature (HDT °C.)--was measured according ISO 75 atapplied forces of 0.45 and 1.8 MPa--the mean of the two readings at eachtemperature is given.

EXAMPLE 1

A series of filled polymer formulations was made up and tested. Thematerials produced were formulated as similar to vehicle interior trimmaterials. The raw materials of the formulations used are set out inTable 1 below. Amounts of the materials used are given as parts byweight (pbw). The formulations were made up by thoroughly dry blendingthe components and then melt processing in a twin screw extruder andcooling and chopping the lace to give pellets.

The polypropylenes used were PP-B and PP-C (MFI's given); thepolyethylene was PE-A; the filler used was talc 20 M00S and thefollowing additive mix (Add) was used in each run:

    ______________________________________                                        Material         pbw                                                          ______________________________________                                        Irganox 1010     0.25                                                         Tinuvin 770      0.50                                                         Crodamide E      0.25                                                         Epoxy resin (solid)                                                                            0.50                                                         Zinc stearate    0.16                                                         Dark grey pigment mix                                                                          0.67       Total 2.33                                        ______________________________________                                    

Run 1 was a control run using a medium impact polypropylene copolymer(co-PP) instead of the blend of polypropylene and polyethylene used inthe runs of the invention. This control is broadly comparable withcurrently commercially available polypropylene copolymer formulationsintended for vehicle interior trim and similar applications. In Runs 2,3, 4, 5 and 9 the polypropylene and polyethylene were blended in anextruder and pelleted before use in the formulation (i.e. the polymersoverall had two passes of melt processing). In run 5 a liquid epoxyresin was used and the additive mix was added to and thoroughly dryblended with the polymer and filler components before the PDMS wasadded. In run 20 a high rubber EPR copolymer was included to improve thetoughness.

Test samples were injection moulded using the pellets. The results oftesting are set out in Table 5 below. Runs 2 to 4 illustrate the effectof increasing filler content. At lower or comparable filler contents,the runs of the invention are clearly superior to the control. Run 4using 30% filler shows but marginally poorer scratch resistance than thecontrol at 20% filler. Run 5 includes PDMS and shows a further increasein scratch resistance. Runs 2 to 6 use a MFI 6 and Runs 7 to 10 a MFI 13polypropylene. The results indicate no significant difference betweenthe two pass melt processed and single pass materials. Run 10 indicatesthat the toughness can be improved whilst sacrificing a little onscratch resistance.

                  TABLE 1                                                         ______________________________________                                        Run  Ex    PP         PE   Talc Add  Other                                    No   No    MFI    pbw   pbw  pbw  pbw  pbw   Material                         ______________________________________                                        1    C1    13     77.67 --   20   2.33       PP is co-PP                      2    1      6     70.27 12.40                                                                              15   2.33                                        3    1      6     66.02 11.65                                                                              20   2.33                                        4    1      6     57.52 10.15                                                                              30   2.33                                        5    1      6     64.32 11.35                                                                              20   2.33 2.0   PDMS                             6    1      6     66.02 11.65                                                                              20   2.33                                        7    1     13     66.02 11.65                                                                              20   2.33                                        8    1     13     58.52 19.42                                                                              20   2.33                                        9    1     13     66.02 11.65                                                                              20   2.33                                        10   1     13     55.12 10.90                                                                              20   2.33 11.65 EPR                              ______________________________________                                    

EXAMPLE 2

A comparison was run between a PDMS containing formulation as describedin our PCT Application No PCT/GB 92/01400 (published as WO 93/ . . . A),Run 11, and a formulation of this invention, Run 12, containing no PDMSand made using PP-B and PE-A. The raw materials of the formulations areset out in Table 2 below. The formulations were made up as described inExample 1 (in the Control the epoxy resin was added to the mix and dryblended in before the PDMS was added).

                  TABLE 2                                                         ______________________________________                                                        Amount (pbw)                                                  Material          Run 11 (C2)                                                                              Run 12                                           ______________________________________                                        co-PP MFI 13      73.97      --                                               PP-B MFI 6        --         64.15                                            PE-A MFI 13       --         11.32                                            Talc 20 MOOS      22         22                                               PDMS              2.0        --                                               Epoxy resin (liquid)                                                                            0.5        0.5                                              Irganox 1010      0.1        0.1                                              DSTDP             0.1        0.1                                              Tinuvin 770       0.5        0.5                                              Crodamide E       0.5        0.5                                              Zinc stearate     0.16       0.16                                             Dark grey pigment mix                                                                           0.67       0.67                                             ______________________________________                                    

Test samples were injection moulded using the pellets from extrusionmixing. Scratch resistance testing showed that the Run 2 formulation wasconsistently superior to that of the Run 1 control, particularly atloads above about 5N. The results of physical testing these twoformulations are included in Table 5 below. These results indicate thatthe formulation of this invention has better resistance to stresswhitening than the control.

EXAMPLE 3

A further series of filled polymer formulations was made up and tested.The materials produced were formulated as similar to domestic appliancematerials, particularly to have high gloss. The formulations used areset out in Table 3 below. In the Example Runs (14 to 17) PP-C and PE-A,talc Finntalc M03, medium grey pigment mix (1 part per hundred of totalcomposition) and the following Additive mix were used:

    ______________________________________                                        Material         pbw                                                          ______________________________________                                        Hostanox OB      0.12                                                         Hostanox SE 10   0.36                                                         Epoxy resin (solid)                                                                            0.50                                                         Zinc stearate    0.18                                                         Crodamide E      0.50       Total 1.66                                        ______________________________________                                    

The formulations were made up by thoroughly dry blending the componentsand then melt processing in a twin screw extruder and cooling andchopping the lace to give pellets. The formulated polymer mix had a MFIof about 7 to 9.

                  TABLE 3                                                         ______________________________________                                        Run   Ex     PP      PE   Talc  Add  Other                                    No    No     pbw     pbw  pbw   pbw  pbw   Material                           ______________________________________                                        13    C3     88.34   --   10    1.66       PP is co-PP                        14    3      75.09   13.25                                                                              10    1.66                                          15    3      61.84   13.25                                                                              10    1.66 13.25 EPR                                16    3      75.09   13.25                                                                              10    1.66                                          17    3      79.34   14.00                                                                               5    1.66                                          ______________________________________                                    

Test samples were injection moulded using the pellets. The results oftesting are set out in Table 6 below.

EXAMPLE 4

A further series of filled polymer formulations was made up and tested.The materials produced were formulated with relatively high fillerlevels as similar to vehicle interior trim materials. The raw materialsof the formulations are set out in Table 4 below. The filler used wastalc 20 M00S and the following additive mix (Add) was used in each run:

    ______________________________________                                        Material         pbw                                                          ______________________________________                                        Irganox 1010     0.25                                                         Tinuvin 770      0.50                                                         Crodamide E      0.25                                                         Epoxy resin (solid)                                                                            0.50                                                         Zinc stearate    0.16                                                         Dark grey pigment mix                                                                          0.67       Total 2.33                                        ______________________________________                                    

The formulations were made up generally as described in Example 1 by dryblending followed by melt processing in an extruder. (NB the pigmentquantity used was 0.67 parts per hundred of the remainder of theformulation.) In runs 18 and 24, 2.0% PDMS was included and the epoxyresin used was a liquid resin which was mixed with the other componentsbefore adding the PDMS. The formulation of Run 25 is a blend of equalparts of extruded pellets of Runs 23 and 7 to give a mix with anintermediate level (about 6% by weight) of the high rubber propyleneethylene copolymer. Run 26 is a Control sample of a commerciallyavailable medium impact copolymer containing 20% talc and a similaradditive and pigment mix to the Runs of the invention.

                                      TABLE 4                                     __________________________________________________________________________    Run                                                                              Ex                                                                              PP      PE      Talc                                                                              Add Other                                            No No                                                                              type                                                                              pbw type                                                                              pbw pbw pbw pbw Material                                     __________________________________________________________________________    18 4 PP-C                                                                              64.89                                                                             PE-B                                                                              11.45                                                                             20  2.33                                                                              2.0 PDMS                                         19 4 PP-D                                                                              66.59                                                                             PE-B                                                                              11.75                                                                             20  2.33                                                 20 4 PP-C                                                                              66.59                                                                             PE-A                                                                              11.75                                                                             20  2.33                                                 21 4 PP-C                                                                              66.59                                                                             PE-D                                                                              11.75                                                                             20  2.33                                                 22 4 PP-A                                                                              66.59                                                                             PE-C                                                                              11.75                                                                             20  2.33                                                 23 4 PP-C                                                                              39.17                                                                             PE-B                                                                              11.75                                                                             20  2.33                                                                              27.42                                                                             EPR                                          24 4 PP-C                                                                              73.21                                                                             PE-B                                                                               8.13                                                                             15  2.33                                                                              2.0 PDMS                                         25 4 (see above)             13.71                                                                             EPR (net)                                    26 C4                                                                              co-PP                                                                             77.67       20  2.33                                                 __________________________________________________________________________

Test samples were injection moulded using the pellets. The results oftesting are set out in Table 6 below.

                                      TABLE 5                                     __________________________________________________________________________    Run                                                                              Ex         Izod     HDT      SR                                            No No                                                                              MFI                                                                              TYS                                                                              FM 23° C.                                                                     -40° C.                                                                     0.45                                                                             1.8                                                                              SG MR Rg                                                                              Lin                                      __________________________________________________________________________    1  C1                                                                              12 27.2                                                                             2.5                                                                              3.3 2.3  110.0                                                                            67.0                                                                             24 9  0 9                                        2  1 9  28.5                                                                             1.9                                                                              4.3 2.1  103.6                                                                            57.8                                                                             49 3.75                                                                             1 5                                        3  1 9  28.3                                                                             2.2                                                                              3.9 2.1  107.4                                                                            63.7                                                                             41 3.75                                                                             1 6                                        4  1 9  27.6                                                                             2.9                                                                              3.1 1.8  110.3                                                                            63.4                                                                             18 10 0 8                                        5  1 8  25.5                                                                             2.1                                                                              4.9 2.3  106.0                                                                            60.9                                                                             18 1.25                                                                             1 4-5                                      6  1 10 28.4                                                                             2.2                                                                              3.4 2.3  110.2                                                                            59.9                                                                             34 7.25                                                                             1 7                                        7  1 13 29.2                                                                             2.5                                                                              3.0 1.9  111.0                                                                            64.6                                                                             33 5  2 6                                        8  1 14 25.6                                                                             1.9                                                                              3.2 2.0  100.7                                                                            56.5                                                                             33 3.5                                                                              2 5                                        9  1 14 28.7                                                                             2.3                                                                              2.9 1.8  109.1                                                                            63.4                                                                             32 7.75                                                                             1 7                                        10 1 12 26.3                                                                             2.1                                                                              3.9 2.1  104.5                                                                            58.5                                                                             36 5.5                                                                              1 7                                        11 C2                                                                              13 23.5                                                                             2.7                                                                              3.9 --   111                                                                              62 -- -- --                                                                              --                                       12 2 9.6                                                                              26.1                                                                             2.5                                                                              3.3 --   109                                                                              59 -- -- --                                                                              --                                       __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Run                                                                              Ex          Izod   HDT        SR                                           No No                                                                              MFI TYS                                                                              FM 23° C.                                                                     0° C.                                                                     0.45                                                                              1.8 SG MR Rg                                        __________________________________________________________________________    13 C3                                                                              7   27.8                                                                             1.8                                                                              8.1 5.2                                                                              100.9                                                                             57.0                                                                              53 5  0                                         14 3 9.4 31.2                                                                             1.8                                                                              5.1 2.5                                                                              95.7                                                                              57.0                                                                              67 2.2                                                                              1                                         15 3 6.8 27.2                                                                             1.5                                                                              9.1 4.0                                                                              91.6                                                                              53.3                                                                              69 1  0                                         16 3 9.5 31.2                                                                             1.8                                                                              5.3 2.7                                                                              96.6                                                                              57.3                                                                              70 4  0                                         17 3 9.3 31.4                                                                             1.6                                                                              6.3 2.8                                                                              94.9                                                                              55.0                                                                              73 2.8                                                                              1                                         18 4 13  28.9                                                                             2.5                                                                              3.1 2.3                                                                              107.3                                                                             61.2                                                                              15 2.25                                                                             1                                         19 4 29  30.2                                                                             2.5                                                                              2.5 1.9                                                                              107.7                                                                             61.7                                                                              20 6.5                                                                              1                                         20 4 --  32.4                                                                             2.6                                                                              2.7 2.1                                                                              108.6                                                                             63.4                                                                              17 4.5                                                                              1                                         21 4 --  32.3                                                                             2.5                                                                              2.6 2.0                                                                              106.5                                                                             61.2                                                                              20 2.75                                                                             3                                         22 4 3.2 31.6                                                                             2.5                                                                              4.9 2.3                                                                              90.6                                                                              64.5                                                                              20 5.2                                                                              3                                         23 4 11  22.3                                                                             1.7                                                                              8.1 4.1                                                                              113.0                                                                             56.7                                                                              20 7.75                                                                             1                                         24 4 --  30.2                                                                             2.2                                                                              3.3 2.3                                                                              96.9                                                                              61.6                                                                              29 1  0                                         25 4 --  30.1                                                                             2.1                                                                              3.8 2.5                                                                              97.2                                                                              59.2                                                                              19 5  5                                         26 C4                                                                              20  25 2.5                                                                              3.3 -- 112 62  17 9  0                                         __________________________________________________________________________

We claim:
 1. A method of producing a filled polymer composition havingas a major component a polymer resin blend of from 70 to 95% by weightof a polypropylene homopolymer, from 5 to 30% by weight of a low densitypolyethylene having a density in the range of about 0.89 to 0.935,from 5to 30% by weight of talc; at least 0.5% by weight of the polymer resinblend of a polyorganosiloxane; and an epoxy resin, which methodcomprises mixing the talc and the epoxy resin prior to mixing withanother component of the composition which is significantly absorbed bythe talc, mixing the epoxy resin with the talc prior to addition of thepolyorganosiloxane and subsequently mixing the components of thecomposition in the melt phase and extruding the composition.
 2. Themethod of claim 1, wherein the polypropylene homopolymer has a melt flowindex of from 2 to 50 dg.min⁻¹ at 230° C., 2.16 kg load.
 3. The methodof claim 1 wherein the low density polyethylene is a linear low densitypolyethylene or a very low density polyethylene.
 4. The method of claim1 wherein the low density polyethylene has a melt flow index of from 2to 40 dg.min⁻¹ at 190° C., 2.16 kg load.
 5. The method of claim 1,wherein the relative proportions of polypropylene homopolymer and lowdensity polyethylene are from 80 to 90% polypropylene and 20 to 10%polyethylene.
 6. The method of claim 1, wherein the amount of talc isfrom 14 to 30% by weight of the composition and the polypropylene has amelt flow index of from 10 to 50 dg.min⁻¹ at 230° C., 2 16 kg load. 7.The method of claim 6, wherein the amount of polyorganosiloxane is from0.5 to 2.5% by weight and the polyorganosiloxane having a viscosity offrom 13000 to 50000 cSt at 25° C.
 8. The method of claim 1, wherein thepolymer composition additionally includes from 0.1 to 0.8% by weight ofthe total composition of a fatty acid amide.
 9. The method of claim 1,wherein the polymer composition additionally includes one or moreof:from 0.1 to 7% of one or more pigments; from 0.05 to 0.7% of one ormore hindered phenol antioxidants; from 0.05 to 1% of one or moreantioxidant thioester synergists; from 0.05 to 0.8% of one or moreneutralizing or antacid agents, and/or about 0.8% of one or more ultraviolet light stabilizers, all percentages by weight being based on theweight of the total composition.
 10. The method of claim 1, wherein theamount of epoxy resin is from 0.5 to 2% by weight of the totalcomposition.
 11. The method of claim 1, wherein the amount of epoxyresin is from 0.4 to 1% by weight.